The most commonly employed bicycle brake assemblies are cantilever/caliper brakes in which brake arms are pivotally mounted to the bicycle frame and displaced by a cable so that brake pads engage the rim of the bicycle wheel. A handle bar-mounted, manually-engageable lever is used to displace the brake cable and actuate the brake assembly. Such brake assemblies usually employ bell crank brake arms which are coupled to the actuating cable by a variety of techniques. Most typically, an inverted V-shaped length of cable is centrally connected to the actuating cable at the upper end and is connected to the opposed brake arms at the two lower ends. Upward displacement of the actuating cable causes the motion to be transmitted through the V-shaped cable to the brake arms, which in turn are pivoted and moved into braking engagement with the bicycle wheel rim.
Such prior art structures have numerous disadvantages. Initially, most of them require a large number of components which must be coupled together by fasteners of various types and are tedious to adjust, maintain and replace. Moreover, and very importantly, as the number of components and couplings between components increases, the overall safety and reliability decreases. In many areas, the failure of a single component or fastener can cause the entire brake assembly to fail.
U.S. Pat. No. 4,969,539 illustrates several different types of cantilever/caliper bicycle brake assemblies and the various schemes for coupling the brake actuating cable to move the brake levers. Each of these assemblies, including the patented invention, employs a large number of components and is based upon connecting the actuating cable to the lever arms through the use of connecting rods or cable members. French Patent No. 986,791 similarly employs an inverted V-shaped length of cable to connect the actuating cable to the brake arms.
Another approach which is found in the patent literature is to couple the brake actuating cable to an inverted U-shaped resilient band member. The resilient band is used as a return mechanism which biases the lever arms to a non-braking position. This approach can be seen in British Patent Nos. 317,638 and 450,429. Similarly, French Patent No. 931,970 employs such a band structure and British Patent No. 25,466 couples a yoke member to a flexible brake band.
In addition to the continuing proliferation of components, one of the problems common to such band-based actuating yokes is that, as the upper end of the band is pulled upwardly by the brake actuating cable, the band tends to straighten out between its connection to the cable and the lever arms. This causes leverage on the bell crank or lever arms to be reduced with increasing upward displacement. Thus, the brake actuation force is diminished or lost in part when the band member straightens out or unbows.
Brake assemblies which employ flexible cables, of course, have no capacity to bias or return the brake assembly to an open or non-braking position. Thus, auxiliary return springs are usually employed in such brakes. Moreover, in order to obtain sufficient leverage, some brake assemblies have arms which extend laterally well beyond the frame of the bicycle so as to be exposed to hooking or catching on objects, which is a safety hazard to the rider and can damage the brake assemblies.
Another problem encountered in prior art bicycle brake assemblies is that the multiple components are subject to relative adjustment by bicycle mechanics or users in a manner which defeats or adversely affects the braking force applied to the wheel rim, as designed by the brake manufacturer. Thus, by shortening and lengthening connecting cables, significant mechanical advantage and braking power can be lost, contrary to the nominal design criteria of the manufacturer.
Accordingly, it is an object of the present invention to provide a brake assembly for a bicycle which has a reduced number of components for ease of manufacture, installation, repair and enhanced safety..
It is a further object of the present invention to provide a bicycle brake assembly which is compact and does not extend laterally of the bicycle frame and yet has a high degree of braking leverage which will not significantly decrease during heavy braking.
Still another object of the present invention is to provide a bicycle brake assembly in which the braking forces designed by the manufacturer are less susceptible to being decreased and defeated during installation and adjustment of the brake.
Another object of the present invention is to provide a brake assembly for a bicycle which uses the inherent resiliency of components to automatically return the brake to the non-braking position when the manual braking force is released.
The bicycle brake assembly of the present invention has other objects and features of advantage which will become apparent from the accompanying drawing and the following description of the Best Mode of Carrying Out the Invention.